course: Potential scattering in metals and unconventional superconductors:strong potentials with finite range
speaker: Kurt Scharnberg (Universität Hamburg, I. Inst. Theoretische Physik)abstract: Strong potential scattering in unconventional superconductors is an important and frequently discussed topic because it is generally accepted that such defects create states near the gap nodes and thus have a profound effect on the low temperature properties, while at the same time suppressing the transition temperature. To simplify the calculations, the defect potentials are often represented by delta-functions of varying strengths. However, it is elementary to show that delta-function potentials do not scatter free particles in 2 and 3 dimensions. One usually escapes this uncomfortably conclusion by ignoring an infinitely large term, invoking particle- hole symmetry. While this uncontrolled approximation gives seemingly reasonable results for delta-functions (s-wave scattering only), physically unacceptable results ensue, when scattering in many angular momentum channels are considered. For a correct treatment, that reproduces analytic results for simple examples (e.g. hard sphere), the energy dependence of the matrix elements of the scattering potential need to be fully taken into account. Since high-temperature superconductors can be treated as two-dimenensional systems, albeit with anisotropy in the plane, a two-dimensional integral equation for the T-matrix needs to be solved, which is far from trivial. We present results for the local density of states near a single defect and for the selfenergy parts in the case of an ensemble of randomly distributed defects.
timetable:
Mon 23 Jul, 9:00 - 10:30, Aula Dini
Tue 24 Jul, 11:00 - 12:30, Aula Dini
documents:
Scharnberg1.pdf
Scharnberg2.pdf
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